ACUTE RENAL FAILURE DEFINITION: Acute kidney injury (AKI) is characterized clinically by an abrupt decrease in renal function over a period of hours to days, resulting in the accumulation of nitrogenous waste products (azotemia) and the inability to maintain and regulate fluid, electrolyte, and acid–base balance. Traditionally, AKI has been defined as an increase in serum creatinine (SCr) of more than 0.5 mg/dL when the baseline SCr is less than 2.5 mg/dL, and an increase in SCr of more than 1.0 mg/dL when the baseline SCr is more than 2.5 mg/dL. These criteria are often inaccurate because SCr and glomerular filtration rate (GFR) do not follow a linear relationship. EPIDEMIOLOGY: The epidemiology of AKI varies widely depending on the patient population, geographical location, and the criteria used to evaluate the patient. AKI is generally considered to be an uncommon condition in the community-dwelling population, with an annual incidence of 520 per 100,000 person-years for...